The entire team bonding thing can be over-thought and over-rated by many. Do yourself a favor and don't work this idea too hard. You need to remember, the whole "we are family" concept only runs so deep. The truth of the matter is each individual family has family. If a core group buys into this concept while others go onward with their lives, it can without trying create its own animosity that has a negative effect of/on the team structure.
Girls in general don't "bond" like boys will. Females tend to group in clicks. Your goal as a coach or parent is to make sure the clicks don't have any fuel to dislike another click. It takes very little to set them off. A simple statement "Wonder why they aren't here" is enough to cause doubt and the rumors will travel throughout the tribe. Next thing you know, without trying, you've created the atmosphere the others aren't as serious as yourself so they are not as committed. All so innocent and in the travel ball world it wasn't the intent but becomes a final result.
I have instructed many coaches to leave the social aspects of the experience alone with more focus being on self-improvement of the game itself. The practices and game time, the time spent in the dugout and the field is all you really need to be concerned with. The girls are going to "clump" on their own, especially as teenagers.
It's nice to have the Thanksgiving dinner or Christmas thing we all come to expect, but know to downplay the participation factor. People have lives beyond the field. They have their own families and traditions. You have to respect that. Just don't overthink it. Trying to force the "team bonding" concept on the girls can hurt you as much as it'll ever help you.